Strings of tubulars are frequently supported from surrounding tubulars already run into the wellbore. One way to do that is to set a packer with slips that bite the surrounding tubular and a seal assembly to seal the annular space. Another way to do this is to expand the smaller tubular into a larger surrounding tubular into which it has been run. When so doing, a slip ring delivered on the smaller tubular is employed. As the smaller tubular is expanded, the slip ring is expanded as well until the slip ring contacts the surrounding tubular. At that time the slip ring can get a bite into the surrounding tubular to enhance the connection and to increase the support capacity of the connection.
Prior slip ring designs involved cylindrical shapes that were an open undulating structure of spaced axially oriented elements connected at their opposed ends and defining axially oriented gaps on either side of the axially oriented elements. This made the resulting structure very flexible. It was considered that flexibility was desired in that the resistance to expansion when the tubular within was expanded was kept to a minimum. While that was true, there were other issues with such a design. One issue was structural integrity during storage, when no pipe extended through the slip ring, and later on when running the slip ring into the well on a tubular. The built in flexibility of the prior design proved to be a detriment in those situations. The slip ring could be easily deformed in storage or during run in due to it flexible shape. Another issue was the behavior of the slip ring during expansion. Due the flexible nature of the design, as the tubular inside was expanded with a swage the growth in dimension of the slip ring was irregular resulting in unsymmetrical contact with the surrounding tubular as the swage was advanced. A swage can also be any cone or likewise device designed for expanding a tubular. This tendency of irregular expansion decreased the support capability of the connection after expansion and in extreme situations prevented a fluid tight connection from occurring.
Accordingly what is needed is a slip ring design that is stronger without unduly increasing the expansion force in a tubular that it surrounds while at the same time having more predictable expansion characteristics to enhance the quality and/or capacity of the attachment. These and other features will be described in greater detail in the discussion of the preferred embodiment below as further explained by the associated figures with the appended claims defining the scope of the invention.
An example of flexible rings that can contract due to compression of axial notches is shown in U.S. Pat. No. 5,299,644. Another example of a notched anchor ring that is intended to break into segments at the onset of expansion is illustrated in U.S. Pat. No. 6,793,022.